Ten or 15 years ago, when you bought a compact fluorescent light bulb you might not have been happy with its performance or price. The good news is that much has changed in that time. Many of the standard lamp bulbs we tested could be bought for less than $2, their performance was nearly as good as an incandescent bulb's, and they could save one-third the energy.

There are still some areas where CFL's could improve, including the time it takes for a covered flood/reflector lamp to get to full brightness, compatibility with electronic timers and dimmers, and broadening the applications for ceiling fans, globes, and other specialty bulbs. We run the bulbs through several tests, many of which are based on the Department of Energy's Energy Star qualifications tests. But we typically go beyond the test and provide details on which performed best, not just whether they passed or failed.

Our tests include: Life testing of how long the bulbs will last, putting them through 3-hour on and 20-minute off cycles. Most bulbs make claims of between 6,000 and 12,000 hours. Rapid-cycling testing reflects the average number of 5-minute on and 5-minute off cycles each bulb survived—an especially important test if you use a bulb in a fixture that is turned on and off more than a few times a week. We measure the light output of each bulb in lumens and the color temperature. Those parameters provide an indication of how well it can match the brightness and color of an incandescent bulb. To help predict how accurately colors will appear under different light sources, a Color Rendering Index (CRI) was used. For our bulb evaluations we compare-tested CFL light to the index. If no color shift is seen, it receives a score of 100. Incandescent lights typically score 100 while most CFL only have CRI's of 80—that could make some colors look off.